Let’s assume I have two AD forests. adatum.com & Tailspin.com. Both Forests have there own Exchange 2010 SP3 RU14 Exchange forests. Both domains use a shared smtp address space @mydomain.com . Email inbound for the SMTP space hits a external service provider who then through LDAP query decides which forest to route the emails to.

Now the problem we have is that while we have a shared address space to are two different companies who share a business model. Only one company can register the smtp address space so in the example let’s assume adatun.com goes to o365 and they configure hybrid so as to migrate the accounts and also manage o365 via the hybrid model.

So in this example tailspin.com can’t register a second tenancy with @mydoamin.com since this isn’t allowed. So tailspin need to migrate to the same tenancy which in it’s self is not an issue but the problem we are now faced with is can we configure a second hybrid config between tailspin.com given adatum already have an hybrid config to the tenancy and this is my question, how do we migrate what are two Exchange forests while both running in hybrid?